The content of a register included in a hardware device is typically modified by a software-implemented read-modify-write operation. First, the content of the hardware device register is read out and transferred over an interface bus from the hardware device to memory such as RAM (random access memory) included in an external host. The register content is modified in the memory, for example by setting a bit that activates a certain hardware feature such as turning on a backlight. The bit is typically set with a logic OR operation to avoid changing other bits of the register content. If the bit were instead being cleared, a logic AND operation would be used. After the register content has been changed, the modified content is read out of the memory, transferred from the host device to the hardware device over the interface bus. The target register is then written with the modified content. If the bus used to transfer the register content back and forth between the hardware device and memory is relatively slow, the read-modify-write operation causes bottlenecks for other concurrent operations carried out over the bus. For example, software processes on the same master host or on different hosts may contend for access to the same register data. Also, software processes on the same master host or on different hosts modifying different bits of the same register must perform read-modify-write operations atomically to avoid errors.